The present invention relates to the suppression of electro-magnetic interference (EMI) emissions from an electronic circuit, and more particularly relates to the use of a resident transmission line for the suppression of electrical interferences from an electronic circuit.
Large electronic systems such as main frame computer systems have many EMI problems related to the fundamental clock frequency and its harmonics. Although the source of this radiation can be directly attributed to the delta I switching currents generated on circuit modules of the large system, the noise presents little problem until it is coupled to some form of an antenna. In the case of large systems, the antenna is bus bars used to connect DC power to the circuit module boards. Once the noise exists on the board, it travels on the bus bars and either radiates or couples to cables in their proximity. The noise can then leave the cabinet or box of the computer system by means of cables exiting from the bottom of the computer frame.
To minimize this noise, various techniques have been tried such as covering exiting holes in the computer frames, moving cables from noisy locations, and using conductive paint, gaskets and grommets where applicable. Ceramic decoupling capacitors have also been added to the bus bars where they attach to the circuit module boards.